Thermionic measuring device



Sept. 1933- s. A. scHERBATsKoY El AL 2,129,880

THERMIONIC MEASURING DEVICE Filed June 12,- 193'? v m Y W? 1 n PatentedSept. 13, 1938 'rnnmulomc MEASURING Davies Serge Alexander Scherbatskoyand Jacob. Neu- 'feldfTulsa, Okla.

Application in... 12, 1937, Serial No. 147,996

.Our invention relates to thermionic measurin ievices, and inparticular, to an arrangement for indicatingprogressively andcontinuously the ratio oftwovarying quantities or values.

The primary object of our invention is to provide an apparatus therefor,to accomplish division, wherein the dividend, divisor and their quotientmay be located at distant or adjacent points, in any relative locationwhatsoever, their only interconnection being by means of electricalconductors.

In general, it is an object of our invention to provide a device whichis substantially electrical in nature and which may be constructed in aneflicient and compact manner similar to wellknown electrical measuringdevices or meters, such device thereby taking its place along with thevast number of other electrical measuring devices which are known to theart.

The novel features which we believe to be characteristic of ourinvention are set forth with particularity in the appended claims. tionitself, however, will be better understood by referenceto the followingdescriptiontaken in connection with the accompanying single figure ofdrawing, which represents diagrammatically one of the preferredembodiments.

Referring now more particularly to the drawing, numerals IOa, Nb, andIla, Ilb designate two pairs of terminals at which input voltages E1 andEzare respectively applied. The terminals Illa, Illbare connected to acircuit consisting of a resistance I2 in series with a resistance I3.

The terminals Ila, IIb are connected to a circuit consisting of aresistance I4 in series with a circuit arrangement designated by a blockI 5, the

said circuit arrangement comprising two three electrode tubes I6 and I1connected in push-pull, two resistors I8, I9 connected across the anodesof the tubes I6, I! respectively and a battery 20 inserted between thecathodes of the tubes I6, I1 'and the common terminal of the resistorsI8, I9 respectively. The terminal 2I of I5 is connected directly to oneof the terminals of I3 while the other terminal of I3 and the terminal22 of I5 are respectively connected to the input terminals 28, 24 of aD. C. amplifier 25. The D. C? amplifier' 25 is of a push-pull type wellknown in the art. The output terminal 21 of the amplifier 25 isconnected to the cathodes of the tubes I6, I! and the output terminal 28is connected through the battery 28 to the grids of the tubes I8, II.Both output terminals 26, '21 are also connected to a voltmeter '29. Thevoltmeter is provided with an appropriate scale and is adapted to indiOur inven- 5 Claims. (cl. 171-95) cate automatically and continuouslythe value Ei/E: expressing the ratio of the voltage E1 across theterminals Illa, I0b to the voltage E: across the terminals Ila, IIb.

The operation of this arrangement can be explained as follows:

grid biases, the latter being determined by the voltage between theterminals 28, 21.

Consequently, the voltage between the terminals 26, 21 can be used forcontrolling the equivalent resistance rz of the block Ill, and themagnitude of this voltage determines the value of the resistance 1:. A IThe current flowing from the terminal I-Iia into the resistor I2 inseries with the resistor I 3 and returning to the terminal Illb can beexpressed as follows:

E1 v i l I Assuming that 1'1((R the expression (1) reduces to II=RTI andthe voltage across the terminals oi the resistance I3 can be expressedas, follows:

In a similar manner, the current flowing from the terminal I la' intothe resistor I l and traversing the block I5 from the terminal 22 to theterminal2l and entering into the terminal Ilb can be expressedasfollows? Assuming that r,((R the expression (4) reduces to i as and thevoltage across the terminals 22 and 2| becomes:

The voltages in and or oppose each other in such a manner that thevoltage in across the input terminals 28, 24 of then C. amplifier I! isequal to the difference of m and 0:, i. e.,

and the amplified voltage across the output terminals 28, 21 of the D.C. amplifier is:

where K is the amplification factor.

The voltage or in series with the voltage of the battery 28 constitutesthe grid bias of the tubes I, I1. It is apparent that 04 determines theplate resistance of the tubes and also determines the resistance r: ofthe block I. Under-the conditions shown in the figure the value of n issuch as to render the expression It is seen from the Formula (11) that te magnitude of the resistance "numerically expresses the ratio of thevoltages E1 and E1. This can be derived also in the following manner:

Assuming that the voltage or is proportional to the resistance rs, i.e., let

'where C is the coemcient of proportionality. It

follows then from the expression- (8) that KEfl I zC Assume that theamplification factor K is very large and is such that KEzC/R is largecomparing with one. Then the Formula (12 can be simplified, since thevalue one" in the denominator can be neglected. Then v KIM; I

Consequently, the voltage in isa measure of the ratio 31/13. The degreeof precision of the electronic divider depends upon the amplificationfactor K of the amplifier II and can be increased at will'soas toapproach as nearly as desired the ideal.

It is therefore, seen that the problem of deter- [voltage or across theterminals 26, 21.

mining the ratio of voltages across the terminals Ifla, Illb and Ila,Ilb, is equivalent to determining r2, 1. e., the resistance of the blockI5 between the terminals 2i and 22. On the other hand, the value of r:is controlled and determined by, the

Consequently in the expression (12) instead of measuring the value 1':expressing the ratio Ei/E2 it is sufllcient to determine the voltage orwhich corresponds to the given value of n.

In accordance with the above, the terminals 20, 21 are connected to thevoltmeter 29 which is adapted to indicate directly the value m. It isapparent that to each value of 04 corresponds a determined value of r:and also a determined value of El/E2. Therefore, by changing the scaleof the voltmeter 28 the latter can be adapted to indicate directly thevalue El/Eg'.

It is therefore apparent that we have provided a means for determiningthe ratio of two electrical voltages by applying these voltages to anelectric network comprising two input circuits. One of the inputcircuitsis connected across the terminals Illa, Illb and includes thefixed impedance i des'ignatedby I3. The other input circuit is connectedacross the terminals Ila, IIb and includes the variable impedance 1:desisnatedby the block I5. The variable impedance is controlled by. thevoltage across the terminals 28, 21. The voltage drops acrossthelmpedances 1'1 and r: oppose each'other'and the difference between thesevoltages controls the voltage across the terminals 28, 21 and causes thevariable im-.

pedance r: to change its, value'so as to decrease the magnitude of thesaid difference. The ratio of the electrical input voltages isdetermined by the value of the variable impedance n and on the otherhand the value of the impedance 1'; is indicated by the voltmeter 28.v V

It now the relative values of the voltages E1 and E: change, thevoltmeter 28 will indicate a new value oithe ratio Er/Ez and, ingeneral, in case of varying input voltages the voltmeter 2' willindicate automaticallyandcontinuously the instantaneous value of theirratio.

Assume for instance that the voltage E2 increases and the voltage E1 ismaintained constant. 'Then the current i: and the voltage on will alsoincrease, and will cause a'correspcnding variation of the voltage n.Then the amplified voltage or derived from the output terminals of 25changes its value in such a manner as to-cause a decrease of theresistance r: of 'theblock Ii. Then the voltage drop on across there'sistor 1: becomes again substantially equal to the voltage drop 01across the resistor 11 so that the relation (10) is again substantiallysatisfied. Itshould be noted however that in this case the resistance1': has a diiferent and a smallervalue which corresponds to a new and asmaller value of the ratio El/E2. To this new value of r: correspondsthe new value of or which is directly indicated by the voltmeter 28.

It is apparent that the above described circuit is not capable ofdetermining the exact'value of the ratio of the voltages E1 and E2.Assume, for

instance, that.the conditions approach very closely an ideal case, i e.,let the error involved in the expression (11) be extremely small. Then.

the voltage 1); determined by (7 will be extremely small and aconsiderable magnification-would be required in order to'make thevoltage or eilective to influence the value ,of the resistance 1'. It istherefore seen that the degree of efiectiveness of the circuit iscontrolled by the circuit constants the amplifier 25) and can beincreased at will to approach as nearly as desired the ideal conditionsof exactitude. obtained in the diagram shown is sufiicient and abundantfor many purposes, but should additional rigor be desired it can readilybe obtained by increasing the voltage amplification of the amplifier' 25or by other suitable means.

It is therefore apparent that we have provided a means -forautomatically and continuously indicating a ratio of two electricalquantities.

In view of our invention and disclosure, variations and modifications tomeet individual whim 15 or' particular need will doubtless becomeevident to others skilled in the art, to obtain part or all of thebenefits of our invention without copying the structure shown, and we,therefore claim all such in so far as they fall within the reasonablespirit and scope of our invention.

It is understood that when reference is made in claims to a ratio of twoquantities it is intended to include in its meaning a value which issubstantially and not always exactly equal to the ratio of the twoquantities and can be considered as representing the ratio for manypractical purposes.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. In an instrument for indicating the ratio of two electrical voltages,an electrical network comprising two pairs of terminals, two impedances,the said terminals being adapted to receive the said voltagesrespectively, means responsive to the said voltages and delivering twocurrents across the said impedances, means responsive to the differencebetween-the voltage drops across the respective impedances for actingupon one of the said impedances in a manner so as to decrease themagnitude of the said difference, and means forindicating the conditionof the said one of the said impedances as a measure of the ratio of thesaid electrical voltages.

2. In a device responsive to the ratio of two electrical voltages, anelectric network comprising. two input circuits, means for applying thesaid voltages to the said input circuits respectively, a variableimpedance in one of the said The degree of exactitude input circuits, afixed impedance in the other of the said input circuits, the said twoimpedances causing voltages to appear across their respective terminalswhen the said two input circuits are subjected to the said two electricinput volt-- ages respectively, means responsive to the difference ofthe voltages across the fixed and the variable impedances for varyingthe variable impedance in a manner so as to decrease the magnitude ofthe said difference, means for indicating the value of the said variableimpedance as a measure of the ratio of the said electrical inputvoltages.

3. In an instrument for indicating the quotient of two electricalvoltages, an electrical network comprising two pairs of terminals, thesaid pairs of terminals being adapted to receive the said voltagesrespectively, means responsive to the said voltages for creatinganunbalan'ce in the said network, means responsive to the said unbalancefor producing another voltage, the said other voltage decreasing themagnitude of the said unbalance, and means for indicating the value ofthe said other voltage as a measure of the said quotient.

4. An indicating system comprising two impedances each connected acrossa source of volt-\ age, an electrical circuitresponsive to thedifierence in the voltage drops across the two impedances for producingan electrical current, means responsive to the said current forcontrolling the value of one of the said impedances in a manner so as toreduce the difierence between the said voltage drops, and means forindicating the magnitude of the said current. a

5. In an instrument responsive to the ratio of two electricalquantities, means for causing the said quantities to produce twoelectrical currents respectively, means responsive to the difl'erencebetween the said currents for changing the magnitude of one of the saidcurrents in order to approach the magnitude of the other current, andmeans connected to the last named means for providing an indication ofthe ratio of said quantities.

SERGE A. SCHERBATSKOY. JACOB NEUFELD.

